1. Field of the Invention
This invention generally relates to asynchronous data collection and, more particularly, to a system and method for collecting image data that is unsynchronized to a camera trigger.
2. Description of the Related Art
FIG. 1 is a schematic block diagram depicting a Picosecond Imaging Circuit Analysis (PICA) test setup (prior art). PICA is a technique that collects near infrared (NIR) light emitted by the hot carriers in a transistor channel. Typically, the integrated circuit (IC) chip under test is electrically connected to a test board. The test board supplies dc power, as well as clock and trigger stimulus signals. The backside of the IC chip may be thinned, and a small area further etched to expose circuitry of interest. A laser scanning microscope and lens may be used to precisely locate the circuitry under investigation, and image data is collected using a high-speed image collection device (e.g., a camera).
If the circuitry under investigation operates synchronously with the clock and trigger supplied by the pulse generator, the image data collection device can be synchronized to circuit operations through the pulse generator. However, depending upon the design and function, the circuitry need not necessarily operate synchronously with respect to the clock and trigger. In that case, the pulse generator cannot supply synchronized points against which the collected image data can be referenced.
It would be advantageous if data from IC circuitry, asynchronously clocked with respect to a camera trigger, could be sampled and retimed to a synchronous clock, to support circuit performance analysis.